Chapter XXXIII: Appendix: Study of the American Buzzard and the “john Crow” (1)

In the preparation of this Memoir, the writer has deemed it best to generally omit any mention of plans and ideas which were brought forth in the work, unless constructions or tests in accordance with them were carried to a sufficient extent to admit of some definite conclusion regarding them. However, owing to the important part played by the warping of the supporting surfaces, or the variation in the angle of auxiliary surfaces, in the methods of preserving the equilibrium of practically all flying machines of the present day, it may be of interest to here add a short mention of the direction in which plans along this line were originally proposed in this work. Mention has already been made of the importance which Mr. Langley attached to the study of the works of the great master-builder, Nature, though recognizing at the same time that owing both to the difference in the forces and methods of construction possible to man, it was not in general possible for him to produce the best results by attempting to too closely imitate the methods or plans of Nature.

Mr. Langley considered it not practicable or best to attempt to imitate the details of construction of the flying mechanism of birds. At the same time, he strongly believed that much was to be learned from them about the practical side of the art of balancing, and he therefore spent a great deal of time both in analyzing the methods practiced by the birds in preserving their equilibrium and in criticizing his own plans in this direction in the light of what Nature would seem likely to do if she had to construct a flying creature on such a large scale. In carrying on his investigations in the art as practiced by the birds, he made a trip to Jamaica during the early weeks of 1900, in order to study the species of buzzard which are so numerous and tame there and are known locally as the “John Crow.” After his return from this trip he wrote the following very interesting letter to Mr. Robert Ridgway, requesting certain data regarding the American buzzard, which he wished to compare with some data on the “John Crow” which he had obtained on this trip:

MARCH 29, 1900. DEAR MR. RIDGWAY:

I have just returned from Jamaica, where among other occupations, I have been studying the evolutions of the buzzard locally called the “John Crow,” a soaring bird which is almost as much superior in skill to our buzzard as that is to a barn-yard fowl in its power of keeping itself in the air without flapping its wings, in what is very nearly a calm.

I have observed particularly the following points with the Jamaica specimen (which I can only give, however, approximately), and I should like to have you give corresponding ones for our Washington buzzard if you can oblige me. [p286]

I note here that the measurements were made on a live bird and that it was impracticable to get the separate weight of the wings except by estimate, but the two wings may be estimated collectively as 1-1/4 lbs., the whole weight being 2-3/4 lbs. to 3 lbs.

Approximate values:

Weight of the bird complete, 3 pounds.
Length of bird, 23 inches.
Spread of wings from tip to tip, 5 ft. 5 in.

Complete curtate area of both wings (that is, the area of the shadow of the bird’s wings when these are fully extended under a vertical sun) is 600 square inches, or nearly 4 sq. ft., consequently each square foot of the bird’s sustaining surface carries 3/4 lbs. Diedral angle nearly 150°.

When the bird is soaring in a nearly calm atmosphere, which it inexplicably does,--soaring I mean nearly in line of the observer’s eyes and coming directly to of going directly away from him,--it presents nearly the following appearance:

√(546)/7 = ‹CP›_2−‹CG›_2.]

‹CP›_2−‹CG›_2 = 3.3 in. = √(546)/7.]

FIGS. 1 and 2.--Type sketches of wings by Holmes from a mean of positions taken from his own sketches and photographs, and also from sketches and photographs by Langley.

‹CP›_2−‹CG›_2−3.6 in. = √(546)/6.5.]

[p287]

I must preface what follows by a little statement of the things which particularly interest me here and which are not a naturalist’s ordinary concern.

First, I want to know the ‹CG› of the bird when in flight. You will understand that though there is but one center of gravity (here symbolized as ‹CG›), it may be considered (1) with reference to its position on the horizontal plan of the bird with wings extended, when it will always be found somewhere in the medial vertical plane, passing through the body, and usually nearly at a certain point with reference to length, the position thus considered being called ‹CG›, or (2) the position of the same ‹CG› with reference to a vertical plane passing transversely through the medial line, the position thus considered being called ‹CG›_2. In the latter case you will understand that the ‹CG› which is that of the whole body, wings and all, will be carried more or less upward when the wings are thrown high up, and will be carried temporarily downward when the wings are at their lowest point of the stroke. It would have a certain position when the bird was at rest and another position when it was soaring and the wings were above the body.

The soaring bird is chiefly held upward by the pressure of the air under each wing, and just as the common center of gravity is a point where all the efforts of gravity are supposed to be centered, so there is a common center of pressure, or one point where all the efforts of the upper pressure of the air may be supposed to be centered, and it will be clear, on very little consideration that this latter point must be always nearly in a vertical line through the ‹CG›, and usually above it. Call it ‹CP›.

‹CG›_1 and ‹CP›_1 are then, the symbols of ‹CG› and ‹CP› as referred to the horizontal plane. ‹CG›_2 and ‹CP›_2 are the symbols for the corresponding ones when referred to their position in the vertical plane.

I shall be glad to explain to you, if you are not familiar with it, the simple method of finding the ‹CG›_1 and ‹CG›_2. It consists in bending the wings into just the position that they would ordinarily occupy above the body in plain soaring flight, keeping them there by a very light bent stick or wire, then hanging the bird up by a line attached to the tip of one wing, and see where this line would pass through the body of the bird, for the ‹CG› will be somewhere in this line. After marking then, on the body of the bird its position, hang it up a second time by the head or tail and note again where the new vertical line runs in the new position. There is but one ‹CG› and but one point in which two straight lines can cross, and that will be the ‹CG› necessarily. Note with all care just where this is above or below the center of the body of the bird.

As for the ‹CP› for either wing, that may be nearly found by tracing the wing on a flat piece of thick paper or cardboard strong enough not to bend much--cutting out the tracing and balancing it well on the point of a pencil--the point about which it balances is very near ‹CP›_2 or the center of pressure in the vertical plane. There is such a point of course in each wing, and when they are thrown up in the actual position that they have in calm soaring flight, we may suppose a horizontal line drawn between them, and it is the distance from this horizontal line to ‹CG›_2 compared with the area of the wings or with the distance between their extended tips which we want to know, which gives the vertical distance which the ‹CG› is below the ‹CP›, the thing we want to know.

It will be very convenient also to have a wing dissected from the body and the wing itself held in about the soaring curve by a bit of light stick balanced on a pencil point, which will give the ‹CG› of the wing as distinct from that of the body. However, the three things I principally want, beside a sketch or [p288] photograph of the bird from about its own level coming directly toward or going directly away in soaring flight, are these:

Approximate weight of the bird,--and approximate tracing of its extended wing with the area, so that we can tell the area of the supporting surface relative to the weight, and finally, the distance between ‹CP›_2, and ‹CG›_2, which is obtainable by the process which I have explained.

I am afraid that what I have just been describing at such length may have a certain obscurity to you, but if you will give me an opportunity, I shall be pleased to illustrate it with the actual experiment when the bird is hung up by a string, and you will see that it is in reality simple.

Referring to the sketches on page 3 of this communication, ‹a› and ‹b› correspond to the centers of pressure on either wing where the upward pressure of the air distributed over each wing may be supposed to be gathered in a single point. This, as I have said, is called the center of pressure with reference to the vertical flight, and its symbol is ‹CP›_2, while the horizontal dotted line between them represents the level of ‹CP›_2, from the best estimate that I could make when the wings are in their natural position of soaring. It is evident that this line passed far above the body of the vulture, and if (the corresponding symbol for the height of the center of gravity being ‹CG›_2), the ‹CG›_2, of the entire bird be taken, it will be found to lie nearly in the point ‹c›. Where ‹c› is in the present case, I could not determine exactly in my hasty examinations in the live bird, but I assume that it is about 1/2 way between the central horizontal axial line of the bird’s body and the upper portion. I repeat that it is important to me to know what the vertical distance is between ‹CP›_2 and ‹CG›_2 in each specimen of soaring bird. I may observe in illustration that in the common sea-gull, it is nearly as shown in the faint sketch; that is to say, that the corresponding line ‹a› ‹b› in the soaring gull passes distinctly through the upper part of the body, and the distance down to the ‹CG›_2 of the whole in the gull is almost nil, while in the buzzard it is very considerable as shown by the corresponding distance in the “John Crow.”

Now, what I want to get from you is the corresponding figures for an average specimen of our Washington buzzard. If you will kindly have one killed and weighed while fresh, and before the rigor-mortis has set in, first noting the position of its wings when soaring in a calm, and (if possible) when coming toward you or going away in about a horizontal plane with your eye, in which position the wings will be elevated and bent somewhat as in the case of the above sketch of the “John Crow”; if you will kindly do this, so as to give me corresponding facts with reference to the buzzard, namely weight, area of extended wing surface, distance between tips as bent up in ordinary flight, distance between ‹extended› tips, ‹the quantity› ‹CP›_2−‹CG›_2, and also will make such a tracing of the buzzard’s wing as Mr. Manly will show you of the “John Crow’s,” I shall be obliged.

My impression is that the buzzard is a considerably heavier bird than the “John Crow,” without, however, very much greater spread of wing. I may observe that when the wings of the Jamaica bird were spread out, they were spread quite to their utmost extent, and the distance between the tips of the terminal feathers was much greater than when in flight. I wish you would kindly also add the scientific name of the “John Crow,” with any particulars that you would think of interest.

If there be any special expenses incurred in the preparation of this memorandum, including the time of a photographer, I will direct them to be paid from the Smithsonian fund. [p289]

If you could get Mr. Holmes (who made most of the sketches and all of the photographs of the “John Crow”), to try and do something like this for your buzzard, especially getting such a photograph of it ‹in flight›, as will give the position of its center of gravity relative to the center of pressure on the wings, it would add very greatly to the value of your memoranda, and I think Mr. Holmes takes so full and intelligent an interest in the subject, that he might be pleased to give his help.

Very truly yours, S. P. LANGLEY, ‹Secretary›.

MR. ROBERT RIDGWAY, Smithsonian Institution, Curator, Division of Ornithology, U. S. National Museum, Washington, D. C.

In response to this request, Mr. Ridgway submitted the following very interesting information:

SMITHSONIAN INSTITUTION, UNITED STATES NATIONAL MUSEUM

WASHINGTON, D. C., October 16, 1900.

PROF. S. P. LANGLEY, Secretary, Smithsonian Institution.

SIR:

I have the honor of submitting herewith the data obtained by Mr. Rolla P. Currie concerning measurements, etc., of the common Turkey Buzzard (‹Cathartes aura›) of the United States, as requested by you in your letter of March 29, last.

The difficulties in the way of securing these data, already explained by me in previous communications, are responsible for the delay in submitting them.

Hoping that this material may prove of use to you, I am,

Very respectfully, R. RIDGWAY, ‹Curator, Division of Birds›.

MEMORANDA IN REGARD TO THE TURKEY BUZZARD (SECOND SPECIMEN)

1. ‹Weight›.--1850 grammes.

2. ‹Area of outstretched wings›.--641 square inches. (Computed from three sheets of tracings, ‹A›_1 and ‹A›_2 comprising the entire area of both wings; ‹B›, a single wing.)

‹Note›.--As the bird was in process of moult, one of the large wing quills, as shown by the tracings and compo-board patterns, is but partially developed, thus slightly modifying the results obtained. Its length, if full grown, would be nearly the same as that of the quill just above it.

3. ‹Distance between the tips of these wings›.--5 feet, 8.7 inches.

4. ‹Distance between the tips of the same wings when the bird is in horizontal soaring flight›.--Estimating the dihedral angle of the wings to be 150°, and elevating the wings so as to make this angle, the distance between their tips [p290] measures 5 feet, 5.7 inches, or 3 inches less than when fully extended in the horizontal plane.

5. ‹The position of the center of pressure of the wing›.--This is indicated on two compo-board patterns, ‹C› and ‹D›. ‹C› was made from a fully extended wing, while ‹D› was made from the wing in the soaring position. The centers of pressure of the wings are about 2 feet, 0.5 inches apart, or 1 foot, 0.25 inches from the central point of the bird’s body.

6. ‹The position of the center of gravity of the soaring bird›.--(Length of buzzard, 26 inches.) The center of gravity of the soaring buzzard in the horizontal plane, CG_1, was found to lie 9-1/2 inches behind the tip of the beak and 16-1/2 inches in front of the tip of the tail.

The center of gravity of the soaring bird in the vertical plane, ‹CG›_2, was found to lie 2.8 inches above the ventral point of the body and 1.6 inches below the dorsal point, the depth of the bird’s body at ‹CG›_1, being 4.4 inches.

In determining the center of gravity, the bird was frozen in the soaring position, its wings making a dihedral angle of 150°. It was then hung up, first horizontally and then vertically, and balanced till the line from which it was suspended coincided with a plumb-line placed in front of it; the measurements were then made.

The bird was afterwards, and while still frozen, hung up in the same way in Mr. Smillie’s photographic room, and exposures made by him in both positions. These photographs, ‹E›_1 and ‹F›_1 were enlarged to natural size, and measurements made on the enlargements yielded, as nearly as could be determined, the same results as when taken directly upon the bird.

As determined by measurements upon the buzzard in soaring position, the center of gravity was found to be 2.65 inches below the center of pressure (estimating the center of pressure to be at the bend of the wing); or, employing the compo-board pattern in a corresponding position, the distance was seen to be a small fraction of an inch less.

7. ‹The position of the root of the wing›.--This is indicated on the tracing A_1.

‹a.› (Depth of the body on a vertical line with root, 3.5 inches.) The root lies 1.6 inches below dorsal line, 1.9 inches above ventral line.

‹b.› (Length of body, 26 inches.) The root lies 7.6 inches behind tip of beak, 18.4 inches in front of tip of tail.

8. ‹The dihedral angle between the wings›.--The photographs taken previously were not sufficiently large or distinct to enable us to determine this with exactness. It was estimated, however, as 150°, and experiments were made on this basis.

9. ‹The center of gravity of the dissected wing›.--This was found, ‹first›, for the wing having all the muscles, up to the ball and socket joint, intact. One of the wings was frozen in the soaring position and its center of gravity found by balancing on a point. Its position was marked by a wire thrust through the wing at this place, and the wing (‹H›) is preserved in formalin. This position is also marked on a special tracing, ‹I›. It lies 6 inches from the base of the humerus bone (root of wing). ‹Secondly›, it was found for the wing denuded of all muscle. Its position was marked on the other wing of the bird, which is preserved dry, spread in the soaring position. It lies 9-3/4 inches from the base of the humerus. [p291]

10. ‹The weight of the dissected wing›.--

‹a.› With all muscle up to the ball and socket joint intact, 325 grammes.

‹b.› With all muscle removed, 190 grammes.

Weight of muscle, therefore, 135 grammes.

‹The position of the root of the tail›.--

‹a.› In the horizontal plane, 11.8 inches in front of the tip of the longest tail feather; 14.2 inches behind tip of beak.

‹b.› In the vertical plane: (depth of body from ventral point below root of tail to a point directly above, which is on a level with the highest point of the back, 2.5 inches.) 1.5 inches above ventral point, 1 inch below dorsal point.

‹Weight of tail›.--With muscle, 40 grammes; ‹without› muscle, 30 grammes. Weight of muscle, therefore, 10 grammes.

EXHIBITS ACCOMPANYING THESE MEMORANDA

‹A›_1 and ‹A›_2. Two sheets, comprising a tracing of the entire turkey buzzard with fully outstretched wings. From these the area of the wings and the distance between their tips was obtained. The position of the root of the wing and the root of the tail is also marked on one of these sheets.

‹B.› One sheet, comprising a tracing of a single wing, and from which the area was also computed. This area, multiplied by 2, gives the same result as the sum of both wings on A_1 and A_2. The compo-board pattern ‹C› was made from this tracing.

‹C.› Compo-board pattern of fully extended wing, on which the center of pressure is indicated.

‹D.› Compo-board pattern of wing in soaring position, on which the center of pressure is shown. [p292]

‹E›_1. Photograph of bird in soaring position, suspended horizontally.

‹E›_2. Same, enlarged to natural size.

‹F›_1. Photograph of bird in soaring position, suspended vertically.

‹F›_2. Same, enlarged to natural size.

‹G.› Tracing of wing in soaring position, from which the compo-board pattern ‹D› was made.

‹H.› Wing preserved in formalin, on which the center of gravity is recorded.

‹I.› Tracing of wing ‹H› when frozen in soaring position, on which the center of gravity is marked.

‹J.› Wing with muscle removed, on which the center of gravity is shown.

Several persons connected with the Smithsonian Institution and U. S. National Museum have contributed towards securing the results herewith submitted. Among them, I desire especially to mention Mr. W. H. Holmes, Mr. [p293] F. A. Lucas, Mr. N. R. Wood, and Mr. R. L. Reed. Mr. Holmes superintended the experiments in connection with ‹No. 6› (finding the bird’s center of gravity), and by his suggestions and criticisms helped me in many other particulars. The photographs and enlargements were made by Mr. T. W. Smillie.

Respectfully submitted, ROLLA P. CURRIE, ‹Aid, Division of Insects, acting in the Division of Birds›.

OCTOBER 16, 1900.

The feats of airmanship performed by the “John Crow” seemed to greatly impress Mr. Langley and shortly after this trip he wrote the following letter to the writer:

SMITHSONIAN INSTITUTION WASHINGTON, D. C., April 16, 1900.

DEAR MR. MANLY:

I am reminded of the consequence that I have, in connection with Mr. Chanute and perhaps Mr. Huffaker, attached in the past to the possibility of directing the bird, and consequently the flying machine, by the mere inflection of the wing, that is, by changing its angle; and you recall to me that Mr. Huffaker at one time proposed to arrange a wing, with some provision of a spring, which should enable it to change its angle automatically. . . . .

I have been noting this ability to guide by the slight inflection of the wing, in my studies of the Jamaica buzzard, and am ready to say that I think, while the quarter-sized working model of the great aerodrome is building, it will be worth while to make some arrangement of the frame or wing-holder which will make it possible to test this idea. I will endeavor to work out something of the kind more in detail myself, but whatever it is, it will apparently involve the ability of the wing to rotate about a line passing nearly through it lengthwise, and an allowance for this; if not in the wing itself, then in the wing-holder; will need to be made while the present model is under construction.

I will request you to especially look out for this, as far as you can on these indications.

Very respectfully yours, S. P. LANGLEY, ‹Secretary›.

The instructions and suggestions contained in this letter and in many conferences on the subject were never carried out by the writer, on account of the extreme pressure of the work already on him which had for its object, not the production of a flying machine which would embody all of the control which we wished it to have, but which would be burdened only with such devices and arrangements as would enable it to transport a human being, and thus demonstrate the practicability of human flight.

[p294]

SECRETARY LANGLEY’S INSTRUCTIONS TO ASSISTANTS

SMITHSONIAN INSTITUTION, WASHINGTON, D. C., November 30, 1895.

DEAR SIR:

The following instructions are to replace those of May 13, 1895:

1. The ‹minimum› fraction of its own “flying weight” (that is, weight complete with initial water and fuel), which the aerodrome shall lift on the pendulum, is 50 percent,[50] under such engine power as can certainly be gotten up in the field and maintained during forty seconds from the time the aerodrome is let go.

The blast, the pumps, and all other essential parts must, in other words, be in such a condition that steam enough for this lifting over 50 per cent of weight can be gotten up readily and surely in the field and in a time which will still leave at least forty seconds’ supply.

2. The ‹minimum› relation of supporting area to weight in any aerodrome constructed hereafter, is to be two feet to the pound,[50] and the minimum of power at the rate of one steadily-maintained horse power[50] at the brake under ordinary conditions, to not over twenty-two pounds (ten kilos) of flying weight. In absence of a brake determination horse power may be taken--

H. P. = (revs. per min. at rest × pitch ×
diameter (in ft.) × thrust (in lbs.)) / 33,000.

These rules do not apply to No. 5, but they do to No. 6, which is to be built over, if necessary, to meet them.

3. In balancing an aerodrome, unless otherwise instructed, set wings at a root angle of either 10°, 7°, or 5°, after being certain from previous inversion and sanding, that the tip angle in motion will not differ from this root angle as much as 5°.

The object in balancing any aerodrome with a single pair of wings is to be able to bring the ‹c g›_2 under their ‹c p›_2 without any reference to the tail, which supports nothing, unless specially ordered. But as this condition cannot now be obtained in Nos. 5 and 6, these at any rate, and perhaps future aerodromes, are to carry a second pair of wings. When this second pair of wings is of nearly equal size with the first it is to be assumed in preliminary adjustments for weight and center of pressure, that the second pair has two-thirds the lifting efficiency per unit area of the first.

Calling the whole distance from the mean center of pressure of the wings to the center of gravity ‹M›. ‹M› is to have a definite relation to the breadth of [p295] wings from tip to tip (‹b›) and total fore and aft length (1), which is provisionally fixed at M = √(bl)/8, and the line of thrust is to be not over one-fourth the way from ‹c p›_2 to ‹c g›_2.

Generally speaking the front pair of wings will be fixed in position and the adjustment for balancing made by moving the rear pair.

The individual weights of all parts checked by lump weighing are to be given by the caretaker (Mr. Huffaker), under the general scheme shown in the note. The work on the aerodromes being divided into two classes, viz.: metal work and all which is not metal, the two in charge of this work (Mr. Reed and Mr. Maltby) are severally responsible for knowing the weight in grammes of any of the parts they have put into their work, giving these weights to Mr. Huffaker, together with any data for filling out the annexed tables,[51] on his request.

Until further orders, Mr. Huffaker is charged with the responsibility of seeing that these conditions are met before any aerodrome is boxed, and will keep the record of weights of the aerodromes and their principal parts as already completed, in a book, to be preserved in your keeping, which will also be arranged to show with signed ‹photographs› and descriptions, and with sketches where needed, the condition and weight (as far as constructed) of every aerodrome, and of any new construction of any part, on the first of each month.

Particular attention is directed to the preceding paragraph, and to the need that evidence of a definite character is to be obtained and preserved of everything already done, and being done.

Without special orders to the contrary, you will not authorize the boxing of any aerodrome which does not, to your knowledge, meet these conditions.

Each aerodrome is to have the following parts in duplicate or in triplicate:

2 pairs wings; 2 pairs tails; 2 pairs light silk covered rudders; 3 pairs wheels;

with any other parts in duplicate or triplicate, which experience has shown to be necessary.

Mr. Reed will not box any aerodrome till a certificate from Mr. Huffaker can be put on the inside cover, with the list of contents, showing what the conditions are as to weight, wing area, power, etc., and the person in the field charged with the duty of launching the aerodrome (at present Mr. Reed), is authorized not to let it go unless he is satisfied that it has a full forty seconds’ supply of steam. [p296]

I am satisfied that a great deal of time is lost in putting the aerodrome together for flight, owing to the absence of any preliminary drill in doing this. Before it goes into the field the whole is to be completely boxed, and then taken out from the box and set up on the clutch, and steam gotten up for flight. All this is to be done in the shop before the final boxing, and provision is to be made so that no wiring or adjusting of parts is to be done in the field which can possibly be avoided by forethought in the shop. The tail-piece, for instance, is to be bushed with brass, so that it will always come into the same place, and make a tight fit, in spite of wetting or shrinking, in the steel tube, where it is to go into a guide-way with a bayonet spring, or a like contrivance for setting it at once securely into position.

The mean positions of the wings and tail are to be laid out in some way permanently on the mid-rod, but every guy-rod or adjustable piece is to be arranged so as to fit at once securely and permanently in its position without wiring or like slow process.

Very truly yours, S. P. LANGLEY, ‹Secretary›.

W. C. WINLOCK, Esq., Assistant in Charge, Smithsonian Institution.

A copy to be communicated to:—
Mr. Huffaker,
Mr. Reed,
Mr. Maltby.

FOOTNOTES.

[37] “The Flying Machine” ‹McClure’s Magazine›, June, 1897.

[38] One noted astronomer and mathematician re-affirmed this opinion as late as 1900 and even stated that man could not hope to construct a flying machine capable of sustaining a weight as great as our largest birds, knowing that even at that time the model Aerodromes Nos. 5 and 6 had already done more than this.

[39] These wings are described in Chapter VI, pp. 191.

[40] See “Experiments in Aerodynamics.” It will be recalled that in the experiments with the “plane-dropper” there was a greatly reduced lifting power with superposed planes when their distance apart was one-half the width the planes, unless a speed of about 42.5 feet a second was obtained. In the above tests with the superposed wings, the speed was only from twenty to twenty-two feet a second at the time of launching, and as the distance between the surfaces was only one-half as great as their width, it is not surprising that the lifting power should not be as great as with the “single-tier” wings.

[41] In fact the setting of the tail at a negative angle and fastening it to the frame by an elastic or spring connection was only begun in 1896, and while it proved to be the key to the solution of the problem of automatic longitudinal stability, yet it was not at that time so recognized, although the first real test of the aerodromes after the elastic connection and negative angle of the tail were adopted resulted in the epoch-making flight of No. 5 on May 6. By comparing the angle of the tail on No. 5 in Plate 27A, Part I, with the angle of the tail on No. 6 in Plate 27B, Part I, it will be seen that while the first had an angle of much less than 5 degrees, the latter had an angle of about 15 degrees. But the wooden springs changed so that it was not accurately known what the angle really was at the time at either flight in 1896.

[42] The drawings, Plate 55, which illustrate many of the fittings used on the frame, show the guy-wires as attached by means of loops twisted in their ends, these drawings having been made before the final plan of attaching the wires had been devised.

[43] See explanation of system of locating points in Part I, Chap. II, p. 15.

[44] See Balancing of Engines, by Archibald Sharpe.

[45] Except for a ten minute stop to renew the supply of lubricating oil and change the sparking batteries.

[46] See foot-note, page 249.

[47] The weight was afterwards increased to 850 pounds due to repairing the wings and adding more sparking batteries.

[48] See Experiments in Aerodynamics, Smithsonian Contributions to Knowledge, Vol. 27, Washington 1891.

[49] Researches and Experiments in Aerial Navigation, Smithsonian Publication No. 1809, Washington, 1908.

[50] All these minimum permissible conditions are connected by the tacit assumption that the supporting area is not greatly over 2 ft. to the pound of weight. If for instance the weight were increased by larger wings or more wings, furnishing a much greater supporting area per pound, these conditions would not necessarily apply.

[51] These tables were later designated as “Data Sheets.” Several copies, with the data duly entered on them, are given in this appendix, and the form which Mr. Langley included in this letter is therefore not repeated here.--EDITOR.

[p297]

DATA SHEETS.

DATA SHEET No. 1.

Weight of Aerodrome No. 5, as photographed on May 11, 1896. Certified to by R. L. Reed, May 6, 1896.

---------------------------------------+----------+-------------+ Parts. | Sizes. | Weight. | ---------------------------------------+----+-----+------+------+ |‹m.›|‹ft.›|‹gr.› |‹lbs.›| 1 Frame, including everything of | | | | | metal, permanent and undetachable, | | | | | such as bed-plate, cross-rods for the | | | | | support of propellers, bearing points | | | | | for clutch, etc. | | | 2443| | | | | | | 2 Engine, gears, shafts, etc. | | | 1110| | | | | | | 3 Pump, pump shaft | | | 231| | | | | | | 4 Hull covering | | | 350| | | | | | | 5 Gasoline tanks, valves | | | 178| | | | | | | 6 Smokestack | | | 342| | | | | | | 7 Float | | | 275| | | | | | | 8 Reel | | | 77| | | | | | | 9 Wing clamps, 235; clamp for | | | | | guy-posts, 29 | | | 264| | | | | | | 10 Other things, counter | | | 75| | | | | | | 11 Burners | | | 360| | | | | | | 12 Boilers | | | 651| | | | | | | 13 Separators, steam gauge, pipe to | | | | | engine | | | 540| | | | | | | 14 Exhaust pipe | | | 143| | | | | | | 15 | | | | | | | | | | 16 | | | | | | | | | | 17 Wings (without clamp) | | | 1950| | | | | | | 18 Tail (without clamp) | | | | | | | | | | 19 Rudder | | | 350| | | | | | | 20 Guy sticks, each, 57 | | | 114| | | | | | | 21 Propellers | | | 800| | | | | | | 22 Extra length of midrod, 308; drop | | | | | piece for rudder, 40 | | | 348| | | | | | | 23 Wood Bowsprit | | | 74| | | | | | | 24 Other things | | | | | | | | | | 25 | | | | | | | | | | 26 | | | | | | | | | | 27 Fuel (at starting flight) | | | 200| | | | | | | 28 Water (at starting flight) | | | 900| | | | | | | 29 | | | | | | | | | | 30 | | | | | | | | | | 31 Sundries unknown | | | | | | | | | | 32 | | | | | | | | | | 33 | | | | | | | | | | 34 Total flying weight | | |11,775| 26 | | | | | | 35 | | | | | | | | | | 36 | | | | | | | | | | 37 | | | | | | | | | | 38 Total area of support (not | | | | | including tail) sq. ft. | |68 | | | | | | | | 39 Total area of support in feet, | | | | | divided by total flying weight in lbs. | | 2.6 | | | | | | | | 40 Total area of horizontal tail sq. | | | | | ft. | | | | | | | | | | 41 Total area of rudder (vertical) | | | | | sq. ft. | | 6 | | | | | | | | 42 Horse-power at brake. Horse-power | | | | | by formula* .72 | | 7 | | | | | | | | 43 Minimum pressure during 40 secs. | | | | | lift, 150 lbs. | | | | | | | | | | 44 Lift at pendulum (during 40 secs. | | | | | absolute) 5772 | | | | | | | | | | 45 Lift at pendulum (during 40 secs. | | | | | in terms of wt.) 49% | | | | | | | | | | 46 Minimum pressure with which wheels | | | | | turn, 10 lbs. | | | | | | | | | | 47 Position of center of pressure of | | | | | wings† F. W., 1575; R. W., 1383.5 | | | | | | | | | | 48 Time of getting up full steam, 1 | | | | | minute | | | | | | | | | | 49 | | | | | | | | | | 50 Curvature of wings, 1/11 | | | | | | | | | | 51 Root angle of wings, 9° | | | | | | | | | | 52 Tip angle of wings, 9° | | | | | | | | | | 53 Position of wings, Front rib on F. | | | | | W., 1607; R. W., 1415.5 | | | | | | | | | | 54 How guyed | | | | | | | | | | 55 | | | | | | | | | | 56 | | | | | | | | | | 57 | | | | | | | | | | 58 Position of tail | | | | | | | | | | 59 Angle of tail | | | | | | | | | | 60 Co-efficient elasticity of tail | | | | | | | | | | 61 Position of rudder, center, | | | | | 1288.3; rear end, 1229.8 | | | | | | | | | | 62 Line of thrust, 2500 | | | | | | | | | | 63 Line of thrust, 1500 which is 9 | | | | | cm. below the center of midrod | | | | | | | | | | 64 Center of gravity_1 of whole, 1497 | | | | | | | | | | 65 Center of gravity_2 2501, i. e., 1 | | | | | cm. above line of thrust | | | | | | | | | | 66 Center of pressure_1 of whole | | | | | estimate, 1498 | | | | | | | | | | 67 Center of pressure_2, 2536 | | | | | | | | | | 68 | | | | | | | | | | 69 | | | | | | | | | | 70 | | | | | | | | | | 71 | | | | | | | | | | 72 | | | | | ---------------------------------------+----+-----+------+------+

Parts. Remarks.

1 Front end of bowsprit, 1686.3.

2 Front end of midrod, 1611.6.

5 Front edge of F. W., 1607.

8 C. of P. on F. W., 1575.

11 Back edge of F. W., 1527.

14 Back edge of cross frame, 1509.

17 Line through center of propellers, 1500.

21 C. of G., 1497.

24 Front edge of R. W., 1415.5.

27 C. of P. on R. W., 1383.5.

30 End of mid-rod, 1360.5.

33 Front end of rudder, 1343.8.

36 Back edge of R. W., 1335.5.

39 Center of rudder, 1288.3.

41 Back end of rudder, 1229.8.

* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000

† This is calculated on the assumption that the center of pressure on each wing or on pair of wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface of the front ones and that the tail proper bears no part of the weight; but if rear wing is smaller or larger this efficiency is smaller or larger per unit of surface.

[p298]

DATA SHEET No. 2.

Weight of Aerodrome No. 6. Certified to by R. L. Reed, November 27 and 28, 1896.

-------------------------------------------+-----------+-------------+ Parts. | Sizes. | Weight. | -------------------------------------------+-----+-----+------+------+ |‹m.› |‹ft.›|‹gr.› |‹lbs.›| 1 Frame, including everything of metal, | | | | | permanent and undetachable, such as bed-| | | | | plate, cross-rods for the support of | | | | | propellers, bearing points for clutch, | | | | | etc. | | | 1178| | 2 Engine, gears, shafts, etc. | | | 1043| | | | | | | 3 Pump, pump shaft | | | 190| | 4 Hull covering | | | 345| | 5 Gasoline tanks, valves | | | 306| | 6 Smokestack, 302; burner, 172 | | | 474| | 7 Float | | | 275| | 8 Reel | | | 77| | 9 Wing clamps, 238; drop piece for rudder, | | | 278| | 40 | | | | | 10 Other things | | | 156| | 11 Boiler, frames, mica cover | | | 694| | 12 Separator, steam gauge, pipe to engines | | | 535| | 13 Exhaust pipe | | | 82| | 14 | | | | | 15 | | | | | 16 | | | | | 17 Wings (without clamp), wet | | | 2154| | 18 Tail (without clamp) | | | | | 19 Rudder | | | 375| | 20 Guy sticks, each 53 | | | 106| | 21 Propellers | | | 644| | 22 Extra length of midrod | | | 398| | 23 Wood bowsprit | | | 135| | 24 Counter | | | 75| | 25 | | | | | 26 | | | | | 27 Fuel (at starting flight) | | | 250| | 28 Water (at starting flight) | | | 2350| | 29 | | | | | 30 | | | | | 31 Sundries unknown | | | | | 32 | | | | | 33 | | | | | 34 Total flying weight | | |12,120| | 35 | | | | | 36 | | | | | 37 | | | | 38 Total area of support (not including | | 54| | | tail) sq. ft. | | | | | 39 Total area of support in feet, divided | | | | | by total flying weight in lbs. | | 2 | | | 40 Total area of horizontal tail sq. ft.| .6 | | | | 41 Total area of rudder (vertical) sq. ft.| .6 | | | | 42 Horse-power at brake Horse-power by | | | | | formula* | | | | | 43 Minimum steam pressure during 40 secs. | | | | 130| lift | | | | | 44 Lift at pendulum (during one minute | | | | 7,211| absolute) | | | | | 45 Lift at pendulum (during one minute in | | | | | terms of wt.) | | | | | 46 Minimum pressure with which wheels turn | | | | 10 | 47 Position of center of pressure of wings†| | | | | 48 Time of getting up full steam, 75 secs. | | | | | 49 Angle of midrod with horizon, 2° 17′ | | | | | 50 Curvature of wings, 1 in 18, 1/4 from | | | | | front | | | | | 51 Root angle of wings, 10° 30′ | | | | | 52 Tip angle of wings, 10° 30′ | | | | | 53 Position of wings | | | | | 54 How guyed | | | | | 55 | | | | | 56 | | | | | 57 | | | | | 58 Position of tail | | | | | 59 Angle of tail | | | | | 60 Co-efficient elasticity of tail | | | | | 61 Position of rudder | | | | | 62 | | | | | 63 Line of thrust 1500 | | | | | 64 Center of gravity_1 of whole, 1483.8 | | | | | 65 Center of gravity_2, 2482‡ | | | | | 66 Center of pressure_1 of whole | | | | | estimate, 1487 | | | | | 67 Center of pressure_2, 2520 | | | | | 68 | | | | | 69 | | | | | 70 | | | | | 71 | | | | | 72 | | | | | -------------------------------------------+-----+-----+------+------+

Parts. Remarks.

1 Front end of bowsprit, 1797.

2 Center of float in first trial, Nov.

6 Front end of midrod, 1613.7. 9 Front edge of F. W., 1595.7.

12 Center of float in flight, Nov. 28, 1896, 1575.8.

16 C. of P. on F. W., 1563.7.

19 Back edge of F. W., 1515.7.

22 Line through center

of propellers, 1500.

26 C. of G., 1484.4 (old C. of G., 1486.3).

29 Front edge of R. W., 1406.

32 C. of P. on R. W., 1374.

35 End of midrod, 1351.3

38 Front end of rudder, 1334.5.

41 Back edge of R. W., 1326.

43 Center of rudder, 1279.

46 Back end of rudder, 1220.5.

49 Reed wings, 80 cm.×185 cm. in rectangle.

53 Weight in shop, 1982 g.

56 On day of flight they weighed 2154 g. because they were damp.

60 Area 54 sq. ft.

63 Spread of wings, 359 cms. or 11′ 9-3/8″.

67 Weight of aerodrome in flight, 12,120 grs.

* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000

† This is calculated on the assumption that the center of pressure on each wing or on pair of wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface of the front ones and that the tail proper bears no part of the weight; but if rear wing is smaller or larger this efficiency is smaller or larger per unit of surface.

‡ This is undoubtedly incorrect, as if it were true, the C. G. would be just at the center of the separator, and this would be impossible. Mr. Reed states that the C. G. was 2 cm. below the side frame, and if this is correct, we would have C. G. = 2486.

[p299]

DATA SHEET No. 3.

Weight of Aerodrome No. 6, Flat Wings and Pénaud Rudder. Certified to by Chas. M. Manly, June 7, 1899.